1. Field of the Invention
The present invention relates to an image forming apparatus having a recording head. The invention also relates to a method of performing a recording head maintenance operation, and a computer-readable recording medium having a program for implementing the method.
2. Description of the Related Art
An inkjet image forming apparatus typically has a recording head that discharges ink droplets via a nozzle onto a recording sheet, thus forming an image on the recording sheet. In such an inkjet image forming apparatus, if the recording head is left standing for a long time after completion of the print operation, the ink around the nozzle may become viscous, or air bubbles may enter the recording head, thereby preventing a normal ink discharge operation. Thus, in conventional image forming apparatuses, it is necessary to perform an appropriate maintenance operation (recovery operation) in order to maintain or recover a normal ink discharging capability of the recording head (see Japanese Laid-Open Patent Application No 2007-136772, for example).
The appropriate maintenance operation may be selected out of a plurality of maintenance operations including blank discharge and head cleaning, depending on the duration of time that the head has been left standing after completion of the print operation. The selected maintenance operation may then be automatically performed at a predetermined timing, which may be set for a fixed time or date, or immediately before a next print operation.
FIG. 1 is a flowchart of a process of determining a maintenance operation for a conventional image forming apparatus. When it is time for a maintenance operation, the image forming apparatus acquires information about the time at which the recording head started being left standing (hereafter referred to as a “standing start time”) (step S11). Then, the image forming apparatus acquires the time at which the recording head ceased being left standing (hereafter referred to as a “standing end time”) (step S12). The image forming apparatus then calculates the duration of time in which the recording head has been left standing (hereafter referred to as a “standing time”) (step S13). The “standing start time” corresponds to the time at which the last print operation was completed. The standing start time may be stored in a non-volatile memory of the image forming apparatus upon completion of the print operation. The “standing end time” substantially corresponds to the time at which the maintenance operation starts, which may be referred to as a “maintenance operation start time”. The image forming apparatus then selects a maintenance operation that is actually performed (step S14), depending on the duration of the standing time calculated in step S13, and then performs the maintenance operation (step S15).
Normally, maintenance operations with greater intensity are selected with increasing standing time. Generally, as the intensity of the maintenance operation increases, more ink is consumed and the operation takes longer. Thus, various methods have been proposed to reduce ink consumption in the maintenance operation, as discussed in Patent Document 1.
In accordance with the above-discussed process, the maintenance operation is selected depending on the standing time that has elapsed since the last print operation was completed. For this reason, if a separate maintenance operation is carried out after completion of the print operation and before the implementation of the automatic maintenance operation, the intensity of the automatic maintenance operation may prove too strong for the level of degradation of the nozzle. In this case, more ink may be spent than is actually required. Furthermore, if the maintenance operation is carried out immediately before the start of a printing operation, an additional wait time may be caused.